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EDWIN F. NOBTHRUP, OF PRINCETON, NEW JERSEY, ASSIGNOR TO PYROLECTEICINSTRUMENT C0., 0F TRENTON, NEW JERSEY, A CORPORATION 0F NEW J EBSEY.

PYBOMETR-IC METHOD AND APPARATUS.

Specication of Letters VPatent.

Patented Dec. 2, 1919.

l.Application led February 28,'1919. Serial No. 279,843.

sought.

My invention resides in an optical pyrometer comprising a member adaptedto be directly inserted into the hot zone or mass Whose temperature ist0 be determined, said member consisting of' transparent or lighttransmitting refractory material Whose one end partakes ofthebtemperature to be determined and accordingly glows, light waves fromthe glowing yend being transmitted through the material itself to apoint or region at a substantial distance from the hot end andpreferably disposed outside of the hot zone or mass whose temperature isto be measured, the light so transmitted causing the distant end of thematerial or member to reproduce, except as affected by absorption withinthe material, the same brightness existing at the hot end. With thebrightness of -this illuminated cold end may be compared the brightnessof an incandescent lamp filament, the current through which is adjusteduntil the brightness of the lamp filament corresponds with 'thebrightness of the cold end of the refractory material or member, thecurrent in f the lamp filament when equality of brightness has beenobtained, being measured and serving as an indication or measure of thetemperature of the hot end of the refractory member.

My invention resides in pyrometric method and apparatus of the characterhereinafter described.

For an illustration of one of the various forms my invention may take,reference is to be had to the accompanying drawing, in

. which Figure 1 is a longitudinal sectional view,

partly in elevation, of pyrometric apparatus embodying my invention.

Flg. 2 is a horizontal sectional view, partly in plan, taken on the lineA-A of Fig. 1.

Fig. 3 is a diagram of an electrical circuit which may be employed,andan elemental indication of the relation of a lamp to the refractorymember.

Referringto the drawing, R is a rod of suitably transparent or lighttransmitting refractory material capable of withstanding at its lower orhot end H the high temperatures to be measured. By preference, the rod Ris of quartz andmay be of circular or any other suitable cross section.The rod R i is made of any suitable length, and preferably of lengthgreat enough to have its upper or cold end Cssuiiiciently remote fromthe hot zone or mass whose temperature vis to be measured for thecomfort and convenience of the observer. v

The rod R is preferably housed within the tube B of any suitablematerial, as metal. A lining D of asbestos or similar packingintervening between the rod R and the inner walloofthe tube B may beemployed. The tube B may be threaded as indicated at a,

ing the cover or upper end closure d in which is threaded the threadedbarrel e of the optical system comprising the lens f and eye piece g,this o adjustable longitudinal y by rotating the same with respect -tothe cover d, for focusing purposes.

In the chamber E is an aperture h through which extends a lamp socket ilongitudinally disposedv in the sleeve j secured to the chamber E. Heldin the socket i is the incandescent lamp L having the filament k. Oneterminal of the filament lc communicates with the lamp base Z which isin electrical communication with the socket i and through it with themetal chamber E, with which is connected one circuit conductor m. Theother circuit conductor n communicates with the other terminal of thelilament c.

'As indicated in Fig. 3, the lamp is in cir'- cuit with any suitablesource ofcurrent, as a battery S, ammeter or milliammeter M andadjustable resistance or rheostat r.

.PThe galvanometeror current measuring into the lug b on the bottom o'of a light excluding box or chamber E havtical system being instrument Mmay' be of the well known DArsonval type. Since substantial current canflow through the filament c Without causing it to glow and therefore tobe useful in a relation of the character herein described, the springcontrol of the moving coil of the instrument M may be so adjusted thatthe actual zero of the instrument is suppressed or to one side of thelow end of the instrument scale, the needle or pointer v of theinstrument coming to rest against a stop t when pointing at the low endof the scale.

The mode of operation is as follows;

The hot or fire end H of the rod R is disposed or thrust into the hotzone or into the material whose temperature is to be measured. The end Heventually attains a temperature equal to that obtaining in the hot zoneor mass. It is then glowing, and light from its hot end is transmittedupwardly through it, and causes the upper or cold end C, which may beroughehed or etched, like ground glass, to appear as a luminous spot.whose brightness is dependent upon the brightness at the lower or hotend H. The observer places his eye to the eye piece g and focuses uponthe filament lc whose background is the luminous cold end C of the rodR. The resistance r is then adjusted to cause such current to passthrough the filament Ic that it glows and attains a brightness equal tothe brightness of the cold end C, this coincidence of brightness beingobtained when the impression upon the observer is that the filament k isnot. distinguishable from the surface C. The current for this particularbrightness of the filament lc is measured or indicated by the instrumentM, whose needle defiects toward the right to such point on the scalewhose reading indicates the 'temperature of the hot end H.

The brightness of the cold end C will not be equal to the brightness atthe hot end H, due to absorption of light in transmission from the hotend H tothe end C through the material of rod R. This absorption,however, is taken care of in calibrating the instrument as a whole.

For such calibration the end H may be thrust into molten copper, forexample,

whose temperature of fusion 1s known, and

as the copper cools off amark opposite the needle of the instrument M 1smade uponA its scale at the moment the copper solidifies,

this mark upon the scale corresponding then. with the known temperatureof fusion of` copper. This may be done with several other materials,including for example, platinum, for obtaining another point on thescale at considerably higher temperature.

Obviously, and as understood in radiation pyrometry, the particularfilament or lamp used affects the readings, but the various lamps in thedifferent instruments may be compared with a suitable standard orsubstandard, and accurate calibration obtained in well known manner.

The rod R has been described as and is preferably of the same materialthroughout its length from the hot end H to the cold end C.

However, my invention comprehends also a change of material from the hotend H to the cold end C, so long as the rod or member R as a whole issufficiently light transmitting or transparent. The upper end of the rodin the case of such composite structure may be of glass or lessrefractory material than the lower end H.

' Notwithstanding the fact that the lower end H may on its externalsurface become roughened and opaque, the operation will nevertheless bethat above described, because the interior of the material at the lowerend H will partake of the temperature to be measured and will glow at abrightness corresponding with that temperature; and it is the conditionof the interior of the end H which produces the effect at the cold endC.

As indicated in Fig. 3the rod R may be thrust directly into a mass ofmolten metal G in the container p. Even in the case where upon thesurface of the metal G there is a coating or layer of slag or othermaterial g, which is at lower temperature than the interior' of the massG, the rod R is thrust through the slag into the hot metal itself, andso an 'accurate reading of ternperature of the metal G may be obtainedwithout effect by the slag g.

Apparatus of the character described is suitable for measuringtemperature throughout a range at whose lower limit is the dullest glowand whose upper limit may be anything which is not beyond a temperaturedestructive of the material of which the end H of the member R iscomposed, and which is not beyond the temperature destructive of thefilament k or other incandescent material used for comparison purposes.

For example, the range of an instrument of the character described maybe from 600 degrees C. to 1800 degrees C.

It will be understood that apparatus embodying my invention may beportable, or may be of such structure that the rod R and suitableassociated elements may be permanently built into afurnace, ceramic ovenor other heating structure whose temperature is to be measured.

When desirable the hot end H of the rod R may be suitably protected byrefractory material of any4 suitable character, as alundum, zircite,etc. This may be desirable where temperature is to be measured undercircumstances where gases or liquid into which the end H.must beinserted are of a .l mass of refractory light transmitting material tothe temperature to be measured,

and producing a temperature indication dependent upon the light due tosaid temperature andl transmitted through said material to anotherpartof said mass.

2. The method of measuring temperature,

which consists in subjecting a portion of a" refractory lighttransmit-ting mass to the temperature to be measured, and producing atemperature indication by Varying the brightness of an incandescent bodyto coincide With the brightness at a remote portion of-said mass due tolight transmitted throughsaid mass and resulting from the temperature tobe measured.

3. Optical pyrometric apparatus com- `prising a mass of lighttransmitting material having a portion adapted to be subjected to. thetemperature to be measured and having a surface remote therefrom towhich light is transmitted through said material, and temperatureindicating means Whose indications are dependent upon the brightness atsaid remote surface.

'4. Optical 'yrometric apparatus comprising a re ractory lighttransmitting structure having a portion adapted to be subjected to thetemperature to be measured and a surface remote therefrom to .whichlight is transmitted through said structure,\and an incandescent bodyWhose brightness is variable to coincide With the brightness at saidsurface.

5..- Optical -pyrometric apparatus comprising a light transmittingmember having an end adapted to be subjected to the temperature to bemeasured andhaving a remote end to Which light due to the temperature ofthe hot end is transmitted through the material of said member, andtempera- 'ture indicating-means Whose indications are deendent upon thebrightness -at said cold en 6. Optical -pyrometric apparatus comprisinga member of refractory light transvmitting material having an endadapted to be subjected to the temperature to be measured and a remoteend to Which light due to the temperature at the hot end'is transmittedthroughA the material of said member, and an incandescent body whosebrightness is variable to coincide with the ness at said remote end.

'7. Optical pyrometric apparatus comprising a quartz rod having an endadapted to be subjected to the temperature to be measured, and means fordetermining the brighttemperature of the hot end by observing thebrightness at the remote end of said lrod due to li ht transmittedthrough said rod from the ot end thereof.

l8. Pyrometric apparatus comprising a refractory light transmittingJmember having an end adapted` to be subjected to the temperature to bemeasured, and means for determining the temperature to which said enmeans Whose indications are dependent upon the light transmitted throughsaid member from said end to a remote portion of said member.

9. Pyrometric apparatus comprising a re ground, means for viewing saidfilament and said remote end, means for varying the current through saidfilament, and a galvanometer Whose deflection is dependent 'upon thecurrent" through said filament.

10. Pyrometric apparatus comprising a rod. of light transmittingmaterial, a light excluding housing Within which an end of said rod isobservable, a tube carried bysaid housingthrough yvhich said rodextends, the other end of said rod adapted to be subjected to thetemperature to be measured, and means for determining said temperaturefrom the brightness at said irst'named end of said rod due to lighttransmitted therethroughfrom the other end thereof.

11. Optical'` pyrometric apparatus comprising a refractory lighttransmitting member having a part adapted to be subjected to thetemperature to be measured, an incandescent filament, a source ofcurrent therefor, means for varying said currentto vary the brightnessof said filament to match the brightness of light transmitted to anotherpart of said member through the material thereof, and a galvanometerhaving ga scale Whose readings are dependent said member'and thebrightness-current characteristic of said filament.

In testimony whereof I have hereunto affxai my signature this 26 day ofFebruary, 19 `t EDWIN NORTHRUP.

is subjected comprising indicating member is visible, an incandescentfilament havmg said remote end for a backiop Aupon the lighttransmitting characteristics

